This invention relates to laundry or dishwasher detergent tablets in the form of cavity tablets, i.e. tablets which have at least one cavity in one of their surfaces. The invention also relates to a process for the production of cavity tablets (or “tabs”). In this process, a cavity is punched into one (generally the upper) side of a large-volume tablet and, in a following process step, may be filled with another material, more particularly by pouring.
The production of cavity tablets involves particular problems because the surface of the tablet is profiled rather than flat. This gives rise to different compression and abrasion conditions for the various surface geometries of the corresponding punch. Since the tendency of substances to be tabletted to adhere to the punch is dependent inter alia on the specific surface pressure and the pressure vectors determined by the surface geometry, certain parts of a punch profile show a particular tendency towards adhesion or caking. After numerous tabletting cycles, such adhesion results in increasing roughness of the tablet surfaces at the corresponding places which can lead to deviations in the quantities of the substances and in addition to tablet breakage. If a tablet breaks in the tabletting press, the production process is seriously disrupted.
One way of solving this problem is to select the geometry of the cavity so that caking and edge breakage at the margins of the cavity are avoided. However, the possibilities for variation are often seriously limited from the technical perspective (for example cavity volume for given tablet dimensions) or the aesthetic perspective. Surface treatment of the punch with anti-adhesion materials can also be used to reduce the tendency towards adhesion. However, the materials known from the prior art are attended by the disadvantage of short useful lives so that the tools have to be changed at frequent intervals. The technical problem addressed by the present invention was to formulate the mixture to be tabletted in such a way—by adding certain substances—that adhesion to the punch and breakages at the edges of the cavity could be reduced or avoided altogether. According to the invention, the solution to this problem is characterized in that nonionic surfactants and, in particular, nonionic surfactant mixtures are used in certain quantity ranges in the mixtures to be tabletted. In the case of multiphase (particularly multilayer) tablets, a corresponding addition to the mixture forming the phase which comes into contact during final pressing with the punch forming the cavity in the tablets is sufficient.